debian: Don't install Python modules for obsolete Python versions.

debian: Don't install Python modules for obsolete Python versions.

Python 2.4 is obsolete, not present in Debian squeeze or sid, so don't
install Python modules for it.

It would be better to just put the files directly into
/usr/share/pyshared/ovs/, instead of in site-packages for some specific
Python version, but this causes problems for builds on squeeze, as
documented in commit bc3aa0bf5 (debian: Make python-openvswitch packaging
work with squeeze dh_python2.):

    The dh_python2 helper in Debian squeeze has a limitation that is not
    mentioned anywhere, as far as I can tell: Python files must be in
    /usr/lib/python#.#/site-packages to be installed.  The version in Debian
    wheezy does not have the same limitation.

    This meant that building the Debian packages on squeeze silently produced
    a broken python-openvswitch package, whereas building the same thing on
    wheezy built a working package.

    This fixes the problem by putting the .py files where squeeze expects them.
    It works on wheezy too.

A before-and-after "debdiff" shows that the only significant effect of this
commit is to drop python2.4 symlinks.

CC: horms@debian.org
Reported-by: Luca Falavigna <ftpmaster@debian.org>
Signed-off-by: Ben Pfaff <blp@nicira.com>